Multiply ionization of diethyl ether clusters by 532 nm nanosecond laser: The influence of laser intensity and the electron energy distribution

The formation mechanism for multiply charged ions (C^q+ and O^q+ (q = 2–4)) were investigated using a dual polarity time-of-flight mass spectrometer when diethyl ether clusters interacted with nanosecond laser pulse. The signal intensity of multiply charged ions and electron energy was measured experimentally. It was shown that the intensity of multiply charged ions increased about 50 times when laser intensity increased from 7.6 × 10⁹ to 7.0 × 10¹⁰ W/cm², then saturated as laser intensity increased further. It is interesting that the evolution of the mean value of electron energy was same to that of multiply charged ions. The theoretical calculation showed the ionization potential of atomic ions could be significantly decreased due to the effect of Coulomb screening especially at low laser intensity. It indicated that the electron ionization combined with Coulomb screening effect could explain the production of multiply charged ions in nanosecond laser field.     

Development of single‐drop microextraction and simultaneous derivatization followed by GC‐MS for the determination of aliphatic amines in tobacco

In this work, for the first time, headspace (HS) single‐drop microextraction and simultaneous derivatization followed by GC‐MS was developed to determine the aliphatic amines in tobacco samples. In the HS extraction procedure, the mixture of derivatization reagent and organic solvent was employed as the extraction solvent for HS single‐drop microextraction and in situ derivatization of aliphatic amine in the samples. Fast extraction and simultaneous derivatization of the analytes were performed in a single step, and the obtained derivatives in the microdrop extraction solvent were analyzed by GC‐MS. The optimized experiment conditions were: sample preparation temperature of 80°C and time of 30 min, HS extraction solvent (the mixture of benzyl alcohol and 2,3,4,5,6‐pentafluorobenzaldehyde) volume of 2.0 μL, extraction time of 90 s. With the optimal conditions, the method validations were also studied. The method has good linearity (R² more than 0.99), accepted precision (RSD less than 13%), good recovery (98–104%) and low limit of detection (0.11–0.97 μg/g). Finally, the proposed technique was successfully applied to the analyses of aliphatic amines in tobacco samples of seven different brands. It was further demonstrated that the proposed method offered a simple, low‐cost and reliable approach to determine aliphatic amines in tobacco samples.     

槲皮素在悬汞电极上的伏安行为研究

应用循环扫描伏安法考察槲皮素在悬汞电极上的电化学行为,并用线性扫描伏安法测定其含量。在0.1mol/LNa2CO3-NaHCO3(pH9.51)缓冲溶液中,槲皮素在-1.33V(vs.Ag/AgCl)处出现灵敏的还原峰,峰电流与其浓度在2.0×10-6～2.0×10-5mol/L(r=0.9989)范围内呈良好的线性关系。该方法可直接用于罗布麻叶中槲皮素的含量测定。     

光网络中光纤光栅构成的波长分插复用器理论及进展

本文从光网络角度详细叙述、分析了各种光纤光栅构成的波长分插复用器技术的发展及理论 ,并指出了不同种类分插复用器各自适用的范围 ,表明了光纤光栅构成的波长分插复用器在光网络中的重要性。     

有限长带电导体直线的电荷分布

通过3种方式给出有限长带电导体直线的电荷密度分布,结果表明电荷分布并不均匀.     

超强磁场下非掺杂ZnSe/BeTe Ⅱ型量子阱中激子和带电激子的光学特性

报道了液态氦温度(4.2 K)下非掺杂ZnSe/BeTe Ⅱ型量子结构中ZnSe势阱层内空间直接光致发光(PL)光谱的磁场依赖性(磁场高达53 T).实验结果显示,随着磁场的增加,激子和带电激子的PL强度呈现出相反的振动行为.当激子的PL强度增加时带电激子的PL强度减小,反之,当激子的强度减小时带电激子的强度却增加.并且在整个磁场范围内,这些振动呈现近似等间隔的周期性变化.这个行为被解释为费米能级与朗道能级的周期性共振,这个共振导致了处于费米能级上的二维电子气态密度的周期性调制. 关键词： 光致发光 二维电子气 带电激子 Ⅱ型量子阱     

带电粒子形成胶体晶体的有效硬球模型判据的计算机模拟验证

在对胶体晶体的研究中,带电粒子胶体晶体的形成机理比硬球胶体晶体更加复杂,对其形成条件目前还缺少有效的判断依据. 有效硬球模型判据提出以有效直径作为判断参数. 为了验证该判据的有效性,利用布朗动力学模拟研究了不同有效直径下带电粒子胶体晶体的特性. 为了更加定量地研究单因素对带电胶体晶体形成的影响,取有效直径为2.8至0.8,并对一定的有效直径,研究了粒子几何直径和排斥力不同情况下的结晶行为. 在布朗动力学模拟过程中,采用径向分布函数和键序参数方法检测体系的结构变化,并分析所形成的晶体结构. 结果表明,在判断带电粒子胶体体系能否形成有序结构方面,有效硬球模型判据有一定的合理性. 但是,并不能将有效直径作为唯一的判别参数,而是需要综合其他参数的影响,这显示出该判据的片面性. 关键词： 布朗动力学模拟 带电胶体晶体 有效硬球模型     

Surface tension and density of liquid Sn-Ag alloys

The surface tension and density measurements for Sn-Ag alloys were carried out with the sessile drop method. Seven different compositions were investigated in the range from 0.011 to 0.5 mole fraction of Ag, in a broad range of temperature. With increasing concentrations of Ag, both density and the surface tension are increased. With increasing temperature the density decreases for all of the alloys. A decrease of the surface tension is observed for most of the composition except for the alloy of 0.5 mole fractions of Ag. The obtained results are compared with existing literature data and Butler model calculations and relatively good agreement is observed.     

超临界水流化床流动阻力特性的实验研究

本文在压力23～27 MPa,温度360～420℃的参数范围内,研究了固定床与流化床的流动阻力特性。实验结果表明：传统的计算固定床压降的Ergun公式在超临界水条件下仍可适用,实验值与Ergun公式计算值的平均误差为13.3%。基于固定床及流化床流动阻力特性实验结果拟合了一个适用于超临界水条件下计算流化床最小流化速度的...